1. Field of the Invention
The present invention relates to a vibration device which uses a vibration of a vibration member to generate vibration force.
2. Description of the Related Art
In a vibration device, power is supplied to a vibration member while the vibration member is in pressure contact with a contact member, to generate vibration force in the vibration member, so that the vibration member and the contact member are relatively moved.
In this case, as a method of connecting a power supply terminal of a conventional vibration member, as disclosed in Japanese Examined Utility Model Publication No. 6-28954, one method is to directly bond a lead line, a flexible printed board, or the like on the vibration member with solder.
However, in the above embodiment, since the vibration m ember directly receives heat from the solder, the piezoelectric characteristics of the vibration member are degraded, and satisfactory driving characteristics of a vibration device cannot be obtained.
In a method of directly bonding a power supply terminal to a vibration member with solder, the power supply terminal may be disconnected from the solder, or the solder may peel together with an electrode layer of the vibration member. As a result, the power supply terminal may not be in contact with the vibration member. In addition, when solder is bonded at a position where vibration displacement occurs, a desired vibration mode may be blocked, and sufficient driving force may not be obtained.
Furthermore, both soldering on the vibration member, and providing leads and connections for the terminal for the vibration member to an external drive circuit are cumbersome operations. For this reason, productivity is considerably degraded.
In some vibration devices using a vibration wave, a vibration member having a rectangular shape is vibrated to linearly vibrate a moving member (contact member) which is in contact with the vibration member. Such a vibration device is arranged as shown in FIG. 27, for example. In FIG. 27, reference numeral 271 denotes an elastic member, and reference numeral 272 denotes a piezoelectric element for exciting a vibration of the elastic member 271. The above vibration member is constituted by the elastic member 271 and the piezoelectric element 272.
Reference numerals 272a, 272b, and 272c denote electrode films for applying a voltage signal having a specific frequency to the piezoelectric element 272. Reference numeral 275 denotes a pressure spring for pressing the mobile member 274 against the elastic member 271 with appropriate force, and reference numeral 277 denotes a bearing for reducing an abrasion resistance between the pressure spring 275 and the mobile member 274.
In the vibration device arranged as described above, when a voltage control circuit applies voltages (indicated by sin and cos in FIG. 27) having specific frequencies and phases which are different by 90.degree. to the electrode films 272a and 272b, the piezoelectric element 272 repeatedly extends and contracts at these frequencies. The extension and contraction of the piezoelectric element 272 excites a longitudinal vibration (e.g., primary mode vibration) and a bending vibration (e.g., quaternary mode vibration) in the elastic member 271. These vibrations synthesize a standing wave for moving the mobile member 274. Due to the synthesized standing wave, material points on the surface of the elastic member 271 elliptically move in the same direction. For this reason, when the mobile member 274 is brought into pressure contact with the elastic member 271, the mobile member 274 is driven by friction between the elastic member 271 and the mobile member 274 in the direction indicated by the arrow in FIG. 27. Movement extraction members 273a and 273b amplify the elliptical movement and transmit it to the mobile member 274 arranged on the elastic member 271.
As unit structures of a driving device operate on the basis of the same principle as described above, for example, a structure proposed in Japanese Unexamined Patent Publication No. 2-228266 (see FIG. 28(b)) and a structure proposed in Japanese Unexamined Patent Publication No. 6-261568 (see FIG. 28(b)) are known. In these unit structures, the vibration member 281 and the contact portion between the mobile member 284 and the vibration member 281 are covered with a case 286.
However, in both cases shown in FIGS. 28(a) and 28(b), since the pressure spring 285 for pressing the mobile member 284 against the vibration member 281 is attached to the inside of the case 286, a space for storing the pressure spring 285 must be formed inside the case 286. For this reason, the case 286 tends to increase in size.
The space can be decreased in size by decreasing an amount of deformation by increasing the spring constant of the pressure spring 285. However, when the spring constant is large, the pressing force greatly changes depending on the amount of deformation of the pressure spring 285, and it is difficult to properly set the pressing force.
Also, a unit in which the pressure spring 285 is stored in the case 286 cannot be easily assembled.